Water may be injected into a plurality of locations in a vehicle system to address various issues. For example, water may be injected into an engine intake manifold to humidify the air charge, or into an exhaust manifold to purify the exhaust gas. As another example, water may be injected directly into a combustion chamber for knock control or temperature control. In still other examples, water may be sprayed onto the surface of a vehicle component to clean or cool the component (such as onto a windscreen, a camera lens, a vehicle body, etc.), or to remove particulate matter. Further still, the water may be processed (e.g., filtered or distilled) to provide potable water that can be consumed by a vehicle occupant.
The disbursed water may be sourced from a water generating system present on-board the vehicle. For example, water generated as a side product during vehicle operation, such as during fuel combustion in a cylinder, during operation of an air-conditioning system, due to condensation on a vehicle surface, etc., may be harvested, processed, and stored by the water harvesting system. One example of a water generating system available on-board a vehicle is shown by Martin et al in US20160083936. Additionally or optionally, the water generating system may include an electrically powered water generator that uses electric power to harvest water from ambient humidity. An example of a water generating system coupled to a vehicle is shown by Engel et al. in US20040040322. Therein, the water generating system includes a compressor, an evaporator, a fan, and a condenser, and the system acts largely as a dehumidifier. Air is drawn into the system by the fan. As the air passes over the cold surface of the evaporator, its moisture condenses, and is collected in a reservoir. The air may be reheated via a heat exchanger at the condenser before being released from the system.
One potential issue with such an on-board water generating system is that it consumes power to condense and process the water from the atmosphere. This reduces the fuel economy of the vehicle. The impact may be even larger in vehicles that rely on electrical power to propel the vehicle, such as on battery electric or hybrid electric vehicles (such as BEV's, HEVs and PHEVs). There may also be situations where the electrical power needed to generate the water may conflict with the electrical power requirement for other vehicle functions such as for propelling an electrified vehicle, operating a compressor, regenerating a particulate filter, etc. In the case of water generating systems that rely on trapping condensate from an HVAC system, the water generation requires HVAC operation, which is based on the preferences of a cabin occupant. As a result, there may be situations where HVAC operation is required for water generation, but the cabin occupant does not want HVAC operation.
In one example, the above issues may be addressed by a method for a vehicle comprising: operating a water generator on-board the vehicle using electrical energy to harvest water from ambient air, wherein the operating of the water generator is based on a water level in a water reservoir of the vehicle and excess electrical energy generated on the vehicle. In this way, excess electrical energy generated during vehicle operation can be leveraged for generating water on-board the vehicle.
As one example, a vehicle may be configured with a water generation system for harvesting water trapped in ambient air. The harvested water may be stored in a water reservoir. The water generation system may be operated whenever excess electrical power is available from the vehicle, such as when there is excess regenerative braking energy. For example, during a vehicle deceleration event, regenerative braking energy may be used to charge a system battery up until a threshold state of charge, beyond which the battery cannot accept further charge. If the brake energy available on the deceleration event exceeds the charge accepting capability of the battery, the excess braking energy may be applied to the water generation system. As a result, the need to use friction brakes to achieve a desired level of vehicle braking is reduced. In one example, where the vehicle includes a smart alternator, the alternator may distribute the regenerative braking energy between the system battery and the water generation system as a function of the battery state of charge, and further based on a water level of the reservoir. For example, even if the battery is capable of accepting of a larger portion of the regenerative braking energy, responsive to the water level in the reservoir being lower than a threshold, or in anticipation of water usage over a drive cycle (such as based on navigational input indicative of knock prone engine operation), the larger portion of the regenerative braking energy may be directed to the water generation system. In a further example, if the regenerative braking energy received in the water generation system causes the water level in the reservoir to exceed the threshold, water flow to various water consumers may be increased. For example, water flow to a CCD camera washer, a tire or brake particulate suppressing water nozzle, and a potable water making unit may be increased. Additionally, windshield wiper fluid and coolant fluid levels may be topped off.
In this way, water generation on-board a vehicle may be optimized while improving vehicle fuel economy. The technical effect of using regenerative braking energy to power a water generation system, particularly after a rate capability of a system battery has been exceeded, is that water can be opportunistically generated while reducing the need for friction brakes to decelerate a vehicle. By reducing the reliance on friction brakes, fuel economy is improved and brake life is extended. By proportioning the braking energy, such as via a smart alternator, between charging a system battery and operating the water generation system as a function of the water level in a reservoir on-board the vehicle, water may be made available the vehicle for various water usages. By also adjusting the rate of water usage based on water generation anticipated over the drive cycle, water harvesting via use of regenerative braking energy can be extended over a larger portion of the drive cycle. By relying on excess braking energy to harvest water, reliance on electrical power for harvesting water is reduced. By reducing the need for electrical power, such as from an electric motor of the vehicle, vehicle fuel economy is improved.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.